And that’s not exactly news. Mackey (Michael Chiklis) is always blowing his stack. He explodes so often that, when he wrecks a hospital waiting room (throwing chairs, smashing a plate glass window, etc.) in the fourth episode of the new season of “The Shield,” nobody bats an eyelash.

It’s business as usual for Vic and “The Shield,” which starts its sixth season tonight.

After disappearing for more than a year, “The Shield” is still the same great cop show – so gritty in its realism that the grit gets in your eyes and irritates your skin. The L.A. neighborhood in which Vic and his fellow cops work is so grimy that you still feel like taking a shower after watching them for an hour.

However, you can’t help feeling that you’ve been here before. Vic and his compatriots on the self-styled “Strike Team” are still up to their eyeballs in trouble.

They are perpetually in danger of losing their loved ones, jobs, even their lives. When they’re not being assaulted by thugs on the street, they’re under attack at the ramshackle precinct house where they work, by other cops, superiors and Internal Affairs investigators. All told, they spend more time cleaning up after their own messes than fighting crime.

But if you’ve been watching “The Shield” for five seasons, you already know all this because nothing ever changes.

As the new season gets under way, Vic and his boys are still under investigation by Forest Whitaker. And one of them, Shane Vendrell (Walton Goggins), is struggling with how he’s going to tell Vic about how their friend, Lem Lemanski (Kenneth Johnson), got killed at the conclusion of last season. (In case you forgot, Shane blew up Lem with a hand grenade.)